During the ninth Devil May Cry DMC Mission: Devil Inside, you can collect one secret key: DMC Gold key. It’s very hard and tricky to acquire this key.
The key can be found on the second floor of the building, the one you jump in after your dream.
Secret Key 1 – Gold KeyLocation: Mission 9 – Devil Inside
Required ability/weapon: None / Devil Trigger
Additional Information: The only way to obtain the Gold Key is to use a set of skills that will lift up the creatures into the air. While the creatures are in the air use them as stairs to get to the second floor. Devil Trigger ability that you have learned in your dream just a few moments ago, can be used to acquire the Gold Key easier. Don’t kill all the creatures in the room or you will not be able to reach the second floor and gain the key.